This invention relates to an apparatus and method for cooking cereal grains and particularly to the use of a recycling step as well as use of a vertical cooker for continuously, evenly cooking a grain product while maintaining plug flow.
It is well known in the cooking art to employ vertical cylindrical continuous cookers. A problem the prior art attempts to solve is even cooking of material added to cookers. Cookers of this type have a conical baffle disposed near the bottommost portion of the vertical cooker. In these prior art devices, grain is added to the top of the vertical cooker, which is circular in cross section, and removed from the bottom of the vertical cooker. The temperature of the water in a typical vertical cooker is maintained by a controller, and by use of direct steam injection or use of a steam jacket about the cooker, and the level of water in the cooker is also ordinarily controlled. In particular, it is known to use a vertical continuous cooker having a cone disposed near a bottom portion thereof.
There are several teachings in the prior art of continuous process methods using vertical cookers as a part thereof. In one of these references, U.S. Pat. No. 2,638,838 issued to Talmey et al., an apparatus is shown for heating granular material in a continuous process.
Talmey teaches a method of treating granular material, in a pressurized vessel, including grain, including steps of soaking, de-watering, cooking, again de-watering, dehydrating, and cooling. A float controlled valve is used to maintain constant head of water in tanks. Heated water of 200.degree. F. is used in a mixer. Water is added along the sides of the tanks during cooking. Water separation occurs in the casing of the conveyor, not in the cooker, by way of a perforated section that is surrounded by an auxiliary jacket. The pressure cooker is vertical and has a baffle. Steam jets are supplied to the material as it gravitates downwardly in the cooker. The steam condenses and collects in the bottom of the cooker, the bottom having perforated openings so as to allow water to be drawn off by a pipe to a pump. This vessel is not, however, full of water, but rather steam which condenses and collects at the bottom. Furthermore, since direct steam injection is used, plug flow would be disrupted in this type of device. The water so collected is reinjected into the top of the cooker by a spray nozzle. However, there is no teaching or suggestion of injecting steam into the return water, nor of separating condensed water from the granular material within the vertical cooker, nor of maintaining plug flow within the vertical cooker. Furthermore, although additional treatment steps are shown, none relates to separating the final product and returning that condensate to the vertical cooker to aid cooking and ensure plug flow of the mixture of water and granular material through the vertical cooker. Such plug flow, if relatively uniform, would ensure even cooking of all grains in the cooker.
Another patent, U.S. Pat. No. 3,778,521 to Fisher et al., shows a process for the continuous production of bulgur.
The Fisher et al. patent shows the mixers having conical baffles therein used for the heating and mixing of wheat with water. A variety of control elements and use of steam are shown. However, steam injection appears to occur primarily in horizontal conveyor passage ways, and not in the vertical mixing devices. This differs significantly from the present invention, which doesn't use steam injection within the vertical cooker at all. Such steam injection would also disrupt plug flow if used in a vertical cooker. Moreover, the use of a separator to return liquid to a vertical cooker is not shown or suggested in Fisher nor is true plug flow taught therein.
Another type of continuous process is taught in U.S. Pat. No. 3,132,948 to Smith et al., which teaches a process of producing bulgur. A multi-stage process is shown, including moistening wheat with excess water, tempering, cooking, and drying the product. U.S. Pat. 2,884,327, to Robbins, shows a method of processing wheat. The wheat is subjected to heat and moisture while moving the wheat. These patents fail to teach plug flow using a vertical cooker as part of a process of cooking.
Other patents, while not appearing to be as relevant as the foregoing, are also of interest.
The U.S. Pat. Nos. 911,408, 1,067,342, 129,906, 3,684,526, and 3,944,678, all relate to the controlling of moisture in flour or wheat products. Each of these references relate to a vertical chamber in which a product is received and from which the product exits. The most relevant of these references is to Lowery, U.S. Pat. No. 3,684,526, showing a pipe 36 for injecting a spray mist, not disclosed to be steam, at point 39 so as to slightly moisten the flour to a moisture level of 1.9%. However, there is no suggestion in any of these patents of using water and granular material in pre-mixed form for introduction into a vertical cooker to avoid uneven cooking and to ensure plug flow.